Device for the uv treatment of fluid streams

ABSTRACT

A method of operating a UV disinfection device provided with at least one UV emitter, including supplying the emitter with an operating voltage for a firing and continuous operation thereof, modulating the operating voltage, an operating current, or an electrical power of the UV emitter, detecting the UV radiation emitted by the emitter with a UV sensor that is adapted to temporally resolve the modulation, evaluating the signal recorded by the UV sensor, and checking whether the modulation in the signal given off by the sensor corresponds to a desired value.

The present invention relates to a device for the UV treatment offlowing media, in particular to a device for the UV disinfection ofdrinking water or waste water, having the features of thepre-characterizing clause of Claim 1.

Generic devices are known from the practice, for example from documentsU.S. Pat. No. 5,368,826, U.S. Pat. No. 5,660,719, EP 068 7201 and WO00/40511.

The general technical background of the present invention relates to UVdisinfection systems. A distinction must firstly be drawn between UVdisinfection systems comprising medium-pressure emitters, which are notthe subject of the present invention, and systems of this typecomprising low-pressure mercury UV emitters as specified in thepre-characterizing clause of Claim 1. The systems comprisingmedium-pressure emitters conventionally have few emitter units, whichare distinguished by high UV radiation power with correspondinglyincreased electrical power consumption. As there are, in this case, onlya few emitters, separate monitoring of each individual emitter is easilypossible. In the case of medium-pressure emitters, the cost of thismonitoring is low compared to other expenses and equipment costs.

A significantly larger number of emitters are used in systems comprisinglow-pressure emitters. Although these emitters respectively have lowerUV radiation power, they require lower equipment costs thanmedium-pressure emitters and are also substantially more efficient, thusreducing operating costs. In some cases, systems of this type thereforecomprise several hundred emitters, which are arranged as what is knownas an array in one or more flow channels. These emitters areconventionally used and operated jointly when they are new. The servicelife of emitters of this type is approximately 8,000 to 9,000 operatinghours, i.e. about one year. After this time, the radiation power hasdecreased to the extent that the emitters have to be exchanged. Theemitted radiation power is monitored by UV sensors, which monitor eitherthe entire array or individual selected modules or groups of the array,as in the abovementioned documents U.S. Pat. No. 5,368,826, EP 068 7201and WO 00/40511. These documents do not make provision for individualmonitoring of all of the emitters. In practice, it is assumed that allof the emitters age uniformly.

U.S. Pat. No. 5,660,719 proposes one approach for monitoring individualemitters. In this device, a coil, which receives from the power supplythe electromagnetic radiation of the emitter in operation and which isthen separately evaluated, is allocated to each lamp. The emittedradiation intensity itself is also in this document measured via asingle UV sensor for a plurality of emitters, so the intensity signal isprovided only for the overall array, while the information from theoperating voltage is provided for each individual lamp.

However, monitoring of the individual radiation power of each individualemitter is therefore possible only indirectly, as the supply voltagepath does not provide a clear indication of the emitted UV radiation. Itis therefore conceivable, for example, that, in the case of anelectrical emitter, which is entirely intact from the point of view ofgas inflation, the emitter tube or the cladding tube surrounding theemitter has only limited UV transparency and there is therefore less UVradiation available than is assumed according to the electricalparameters.

The object of the present invention is therefore to provide a device forthe UV treatment of flowing media, in which the radiation power of manylow-pressure mercury emitters is individually monitored.

This object is achieved by a device having the features of Claim 1.

Because provision is made to configure the element for supplying powerto the emitter in such a way that an operating voltage or current thatacts on the emitters during operation, and therefore the radiation fluxfor individual emitters or emitter groups that is emitted by theemitter, may be modulated, and because at least one unit, which isconnected to the sensor means, for monitoring the emitters is configuredto evaluate a modulation contained in the UV radiation that is emittedby the emitters, it may be determined whether an emitter that is actedon by a specific modulation reproduces this modulation in the emittedradiation. A conclusion may thus be drawn regarding the operating stateof the emitter acted on by the modulation. The operating voltage of eachindividual emitter may, for example, be modulated separately in such away that each emitter may be checked individually. This modulation maysimply be an amplitude modulation.

In the case of a method according to the invention for the operation ofa UV disinfection device, the following steps are provided:

a) supplying the emitters with an operating voltage for the purposes ofignition or firing and for the continuous operation of the emitters;

b) modulating the operating voltage of at least one emitter;

c) detecting the UV radiation that is emitted by the emitters using a UVsensor, which is capable of temporally resolving the modulation;

d) evaluating the signal recorded by the UV sensor;

e) checking whether the modulation in the signal issued by the UV sensorcorresponds to a desired value.

This method allows the operating voltage of an individual emitter, agroup of emitters or all of the emitters to be modulated simultaneously.If all of the emitters are modulated simultaneously and the modulationis carried out separately for each emitter (for example, at a differentmodulation frequency), all of the emitters may be monitoredsimultaneously during operation in that the sensor signal is evaluatedwith respect to the various types of modulation and the individualcomponents are filtered out.

It may also be provided that, during operation, the emitters areoperated in a substantially unmodulated manner and, for checking anindividual emitter, only this individual emitter is supplied withmodulated operating voltage. If the modulation is then reflected in thesensor signal, the operating state of the emitter may be determined. Allof the emitters may thus be checked in succession, and this may berepeated cyclically.

The operating voltage of the low-pressure mercury UV emitters has, forexample, a natural frequency in the range from 20 kHz to 1 MHz. Themodulation of the operating voltage is in the form of amplitudemodulation at frequencies in the range from 100 Hz to 100 kHz.

Adjacent emitters may be combined into groups, wherein the emitters ofone group may jointly be modulated at similar frequencies, in particularat frequencies that are adjacent in a frequency grid.

The invention further proposes an electronic power supply unit for alow-pressure mercury emitter, which unit is configured for applying amodulation to the operating voltage or the issued electrical power,preferably as a function of an external control system.

An embodiment of the present invention will be described below withreference to the drawings, in which:

FIG. 1 is a cross section, seen from the side, of a UV disinfectionsystem for flowing water; and

FIG. 2 shows the Fourier-transformed intensity spectrum as generated bythe system according to FIG. 1 during operation.

FIG. 1 illustrates schematically, in a cross section seen from the side,a device for the disinfection of flowing waste water. The flow of wastewater 1 flows in a channel 2, from left to right as shown in FIG. 1. Thewaste water 1 is the outflow of a sewage treatment plant, i.e. wastewater that has already been mechanically and biologically filtered andis substantially transparent, but may still contain microorganisms.

For the purposes of disinfection, UV emitters 3.1, 3.2, 3.3 and 3.4,which are known per se and have the construction of the low-pressuremercury UV emitters, are arranged in the channel 2. These emitters aretubular and extend, in FIG. 1, perpendicularly to the drawing plane,i.e. transversely to the direction of flow of the waste water 1.However, they may also be arranged perpendicularly or longitudinally inthe channel 2. The UV emitters 3 are conventionally constructed in sucha way that cladding tubes made from quartz surround and protect theactual UV emitters from deposits from the waste water and frommechanical damage caused by solids entrained in the waste water. Furtheremitter groups 4.1 to 4.4, 5.1 to 5.4, 6.1 to 6.4, 7.1 to 7.4 and 8.1 to8.4 are arranged downstream of the first emitter group 3. A UV sensor 10is arranged approximately centrally in the emitter arrangement 3.1 to8.4. The UV sensor 10 comprises a silicon carbide diode and iselectrically connected to a control device 11. The control device 11controls a number of electronic series connection or power supply units13 via a connection line 12, an electronic power supply unit 13 beingassociated with each UV emitter. In FIG. 1, four respective power supplyunits are combined to form one unit and are associated with a group offour emitters.

The power supply units 13 supply the UV emitters with an operatingvoltage, which has to have defined current and voltage paths for thepurposes of ignition or firing and for the operation of the UV emitter,via supply lines 14.

For the low-pressure mercury emitters that are conventionally used, thesupply voltage that is issued during operation by the electronic powersupply units 13 is an alternating voltage having a frequency in therange from 50 to 100 kHz.

Because the UV sensor 10 receives, as is known from the prior art,direct and indirect UV radiation from all of the emitters, it may noteasily be determined whether a specific emitter has ignited and isradiating in the intended manner.

In order to determine this, a specific power supply unit 13 is activatedby the control device 11 in such a way that the operating voltage of theemitter associated with this control device is modulated at an amplitudemodulation of, for example, 400 Hz and a range of also, for example,+/−10% of the operating voltage. The intensity, which oscillates at themodulation frequency of 400 Hz, may be detected using the UV sensor 10.Unlike in the case of conventional sensors, the UV sensor 10 isaccordingly not provided with a low-pass filter, which conventionallycuts out frequencies above approximately 20 Hz in order to rule outeffects of the mains frequency (50 Hz or 60 Hz). The UV sensor accordingto the present invention, on the other hand, operates up to frequenciesof at least several kilohertz.

In order to evaluate the intensity signal that is received by the UVsensor 10 and forwarded to the control device 11, this signal isexpediently subjected to a Fourier transformation, for example using theknown FFT algorithm. Using this algorithm, the UV radiation spectrum, asit is received by the UV sensor 10, is broken down in terms of intensityand frequency. FIG. 2 illustrates a spectrum of this type.

In FIG. 2, the Fourier-transformed signal of the UV sensor 10 is plottedas a frequency spectrum. The frequency is plotted on the X-axis, therelative intensity, in arbitrary units, on the Y-axis.

In the case of the exemplary spectrum, the frequencies f3.1, f3.2 andf3.4 have approximately the same intensity, whereas the curve at thefrequency f3.3 has a lower intensity. In the control device 11, thisspectrum would then be evaluated in such a way that the emitter 3.3associated with frequency f3.3 does not convert the modulation signal,which has the same range in the operating voltage of all of theemitters, into a corresponding intensity modulation. This is anindication of the fact that the overall radiation power of the emitter3.3 is lower than that of the other three emitters of the emitter group.

The modulation frequencies of the remaining emitters 4.1 to 8.4 are notshown in FIG. 2. They are located, according to the illustration of FIG.2, at different frequencies. The clarity of the frequency spectrum isimproved if the modulation frequencies of adjacent emitters are similar.A modulation frequency of 400 Hz may, for example, be selected for theemitter 3.1; the emitter 3.2 would receive 450 Hz, the emitter 3.3 500Hz, and the emitter 3.4 550 Hz. The remaining emitters accordingly thenreceive higher modulation frequencies. The respective modulation isclearly allocated to the relevant emitter via the control system 11 andthe individually activated power supply units 13.

Although, in the case of the illustration according to FIG. 2, all ofthe emitters of an emitter group are modulated simultaneously, it mayalso be provided that emitters are modulated individually only for ashort time. A modulation is then, for example, impressed on the emitter4.1, while it is at the same time checked whether this modulation isdetected by the UV sensor. In the Fourier-transformed spectrum, a curvesimilar to that in FIG. 2 then appears, and the absence of this curve isan indication of a failure of the emitter or an associated component.

It may be seen from the illustration of FIG. 1 that not all of theemitters contribute uniformly to the signal received by the UV sensor10. The emitter 3.1, for example, is thus cut off, in the direct line ofsight, from the UV sensor 10, whereas the emitter 5.2 directly suppliesthe UV sensor with radiation. It is therefore to be expected that thesignal that is received only indirectly from the emitter 3.1 provides asmaller contribution to the total intensity received. In order tocompensate this geometrical dependency and to calibrate the monitoringsystem, the following process may be carried out.

Firstly, after installation, all of the emitters may be switched onwithout modulating their operating voltage. The modulation to theoperating voltage may then be impressed individually for each emitterbefore it is checked and recorded what intensity the associated curve(f3.1 to f8.4) has. This curve may then be standardized as a 100% signalfor the relevant emitter. If, over the course of time, the operatingvoltage has to be increased, due to ageing of the emitters, in order toensure a constant UV intensity in the waste water 1 and the modulationis also altered proportionately, the intensity of the respective curvewill not change. It may therefore be checked at any time whether anindividual emitter is producing the provided intensity and whether theemitters of a group or all of the emitters in total are producing auniform power, or whether some emitters decrease in power to a greaterextent than others. Finally, it is possible individually to adjust thepower of the separate emitters in order to achieve a uniform overalldistribution of the radiation intensity in the waste water 1.

In the case of larger systems than the disinfection system illustratedin FIG. 1, it may be necessary to use a plurality of sensors. This isparticularly necessary if a plurality of channels 2, which are opticallyseparated from one another, is provided in the disinfection device.Nevertheless, the advantage is maintained that there is no need for aseparate UV sensor for each emitter and that, owing to the individualmodulation frequency, the individual radiation contribution may bedetermined even during simultaneous operation of other adjacentemitters.

The present embodiment proposed, as the type of modulation, amplitudemodulation at a frequency of several hundred to several thousand hertzand a modulation range of +/−10% of the operating voltage. Other typesof modulation are also possible. The signal may, for example, bemodulated to the operating voltage as a pulse modulation in the form ofa pulse-width modulation. Other methods, which are better adapted to theselected type of modulation than the above-described Fouriertransformation, may then be required for the purposes of demodulation.Band-pass filters, which purposefully filter out the modulationfrequency from the total signal, may, for example, be used.

1-15. (canceled)
 16. A device for the UV treatment of fluids flowing ina flow channel, comprising; a plurality of UV emitters that are disposedin the low channel; at least one UV sensor adapted to monitor anoperating state of the UV emitters; at least one power supply means forsupplying power to said UV emitters, wherein said at least one powersupply means is configured to modulate an operating voltage, forindividual ones of said emitters or groups of said emitters, that issupplied to said emitters during operation; and at least one unit,connected with said at least one UV sensor, for monitoring said UVemitters, wherein said at least one unit is configured to evaluate amodulation contained in UV radiation emitted by said UV emitters.
 17. Adevice according to claim 16, wherein said UV emitters are low-pressuremercury UV emitters.
 18. A device according to claim 17, wherein saidlow-pressure UV emitters are amalgam-type emitters.
 19. A deviceaccording to claim 16, wherein the operating voltage for each of said UVemitters is adapted to be modulated individually.
 20. A device accordingto claim 16, wherein the modulation is an amplitude modulation.
 21. Adevice according to claim 16, wherein evaluation of the modulation isadapted to be effected by means of a Fourier transformation.
 22. Adevice according to claim 16, wherein said UV emitters are adapted to beswitched off individually for purposes of calibration.
 23. A method ofoperating a UV disinfection device provided with at least one UVemitter, including the steps of supplying at least one UV emitter withan operating voltage for a firing and continuous operation thereof,modulating said operating voltage, an operating current, or anelectrical power of at least one of said UV emitters; detecting UVradiation emitted by said at least one UV emitter with a UV sensor thatis adapted to temporally resolve the modulation; evaluating a signalrecorded by said UV sensor; and checking whether the modulation in asignal given off by said UV sensor corresponds to a desired value.
 24. Amethod according to claim 23, wherein said modulating step comprisescarrying out modulation differently for each UV emitter.
 25. A methodaccording to claim 23, wherein during operation said UV emitters areoperated in a substantially unmodulated manner, and wherein for checkingan individual emitter, only such individual emitter is supplied withmodulated operating voltage.
 26. A method according to claim 25, whereinsaid modulating step is carried out successively for all of said UVemitters.
 27. A method according to claim 25, wherein said modulatingstep is repeated cyclically.
 28. A method according to claim 23, whereinfor low-pressure mercury UV emitters, the operating voltage has anatural frequency in the range of from 20 kHz to 1 MHz, and whereinmodulation of the operating voltage is in the form of amplitudemodulation at frequencies of from 100 Hz to 100 kHz
 29. A methodaccording to claim 23, wherein adjacent ones of said UV emitters may becombined into groups, wherein emitters of a given group may be jointlymodulated at similar frequencies.
 30. A method according to claim 29,wherein the emitters of a given group may be jointly modulated atfrequencies that are adjacent in a frequency grid.
 31. An electronicpower supply unit for issuing an operating voltage for a low-pressuremercury UV emitter, comprising means for applying a modulation to theoperating voltage or to issued electrical power.
 32. A power supply unitaccording to claim 31, wherein the modulation is selectable as afunction of an external control system with respect to at least one ofrange, frequency and type of modulation.